1. Field of the Invention
The present invention relates to a method for manufacturing a plate-like alumina powder and a plate-like alumina powder.
2. Description of the Related Art
Patent Literature 1 has disclosed an oriented alumina sintered body formed by using a plate-like alumina powder as a part of a raw material and also has shown that the corrosion resistance and the heat resistance are improved since the alumina sintered body is oriented. However, in order to obtain a high corrosion resistance and a high heat resistance, reduction in amount of impurities in the sintered body is required, and hence in order to further improve the characteristics, a high-purity plate-like alumina powder is desired.
In addition, it has been known that a high-purity and dense alumina sintered body has optical translucency, and Patent Literature 2 has disclosed the optical translucency of a ceramic polycrystalline body having a crystal structure, such as a triclinic crystal, a monoclinic crystal, an orthorhombic crystal, a tetragonal crystal, a trigonal crystal, or a hexagonal crystal. The above literature has shown that in an oriented alumina sintered body formed using a plate-like alumina powder as a part of a raw material, a sufficient heat resistance and a high in-line transmittance can be realized. However, it has been known that in order to realize a high optical translucency by an alumina sintered body, in general, the alumina sintered body is required to have a high impurity, and hence, a high-purity plate-like alumina powder is necessary. As a method for manufacturing a plate-like alumina powder, for example, methods disclosed in Patent Literatures 3 to 5 and Non-Patent Literatures 1 have been known.